1. Field of the Invention
The present invention relates to magnetostrictive transducers for monitoring wall thinning of a pipe, and an apparatus and method for monitoring the wall thinning of a pipe using the magnetostrictive transducers, and more particularly to an apparatus and method for monitoring wall thinning of a pipe using magnetostrictive transducers and a variation in dispersion characteristics of broadband multimode SH waves, wherein the magnetostrictive transducers generate multimode high-frequency shear horizontal (SH) waves, and allow the generated SH waves to travel along the pipe, thus correctly monitoring a status of the wall thinning of the pipe.
2. Description of the Related Art
Typically, “wall thinning” refers to when a wall of a pipe becomes thinner due to corrosion and the like. In association with leakage of a fluid flowing in the pipe, the diagnosis and monitoring of wall thinning is considered to be very important in pipe management. Specifically, in the case where the leakage of such a fluid occurs in a pipe used in a Nuclear Power Plant, there may arise a serious accident, such that strict management and maintenance of the pipe is needed.
The above monitoring of the above wall thinning is one of critical technologies needed for guaranteeing safety of a pipe structure of the Nuclear Power Plant. In order to estimate wall thinning effectively, there is needed an improved technology for diagnosing the presence or absence of the wall thinning and continual monitoring the progress of the wall thinning.
One of promising methods for diagnosing the presence or absence of the wall thinning at high speed and continual monitoring the progress of the wall thinning is to use guided ultrasonic waves.
Guided ultrasonic waves can propagate over long distances, such that they have many advantages in conducting the above diagnosing/monitoring operations. As a result, many intensive researches have recently been conducted into the above method for diagnosing wall thinning of a pipe using guided ultrasonic waves.
However, in order to use guided ultrasonic waves to monitor wall thinning, a variety of problems need to be solved, for example, an appropriate transducer for monitoring should be developed, or the mode identification and the propagation of guided ultrasonic waves in the wall-thinning region should be understood.
Most frequently applied technique for using guided ultrasonic waves is to measure reflected waves from a defect or faulty part. However, this diagnosing method may be effectively used in a specific pipe having an abrupt change in thickness, but a reflection coefficient is not high in gradual thickness variation of a pipe wall, such that it is difficult to monitor the gradual wall thinning which may usually occurs in a pipe elbow due to flow accelerated corrosion (FAC) in Nuclear Power Plant.